Simultaneous Determination of Permethrin andDeltamethrin in Water Samples by Magnetic Solid-phase

Extraction coupled with Dispersive Liquid–LiquidMicroextraction combined with Gas Chromatography

Arezoo Hassan Nooria, Mohammad Rezaeeb, Maryam Kazemipoura andHossein Ali Mashayekhic,*

aDepartment of Chemistry, Kerman branch , Islamic Azad University, Kerman, Iran.bMaterials and Nuclear Fuel Research School, Nuclear Science and Technology Research Institute, Atomic Energy Organization of Iran,

P.O. Box 14395-836, Tehran, Iran.cDepartment of Chemistry, Tonekabon Branch, Islamic Azad University, Tonekabon, Iran.

Received 14 March, revised 7 October 2017, accepted 25 October 2017.

ABSTRACT

In this study, new and efficient method, magnetic solid phase extraction coupled with dispersive liquid–liquid microextracton(MSPE-DLLME) combined with gas chromatography-flame ionization detector (GC-FID) was developed for thepreconcentration and determination of permethrin and deltamethrin in water samples. Several factors influencing the extractionefficiency including amount of sorbent, sorption time, type of extraction solvent and its volume, type of disperser solvent and itsvolume and elution time were investigated and optimized. Using optimum extraction conditions, dynamic linear range of0.5–100 µg L–1 for both, limits of quantification (LOQs) of 0.6 µg L–1 for both and limits of detection (LODs) of 0.01 µg L–1 for bothwere obtained. Finally, the method was successfully applied for the extraction and determination of permethrin and deltamethrinin water samples in the range of micrograms per litre with RSDs < 4 %.

KEYWORDS

Magnetic solid-phase extraction, dispersive liquid–liquid microextraction, permethrin, deltamethrin, gas chromatography, watersamples

1. IntroductionInsecticides on the basis of pyrethrine were first introduced in

the 1950s. Pyrethrines are a class of natural substances whichoriginates from the blossom of the chrysanthemum. Pyrethrineswere, and still are, used as natural insecticides against verminin households. Nevertheless, the production of pyrethrine isexpensive and the resources are limited. For these reasonssynthetic pyrethroids were developed based on the basic struc-ture of natural pyrethrines.1

Synthetic pyrethroids are utilized in households and green-houses, as well as to control fleas and scabies. Moreover, thesecompounds are used for wood and textile protection.2–4 It hasbeen firmly established that synthetic pyrethroids act as power-ful neurotoxic agents.5 The molecular basis for the neurotoxicityof pyrethroids have been attributed to their actions on voltage-dependent sodium channels5,6 and on receptor-regulated chan-nels, like the nicotinic7,8 and GABA-gated chloride channels.9,10

Effects on Ca2+,Mg2+-ATPases have also been reported.11–13

Determination of pesticides in different sample matrices isusually performed after pretreatment steps using either gaschromatography (GC)-mass spectrometry (MS),14 GC-electroncapture and ion trap mass spectrometric detectors,15 GC-nitrogen-phosphorus detector,16 GC-flame photometric detec-tor,17 GC-flame ionization detector,18 or high performance liquidchromatography (HPLC) with different detectors (e.g. MS/MSspectrometry,19 diode array detector).20 The use of ultra-

performance liquid chromatography in detection of pesticideshas also been reported.21

Different preconcentration methods such as solid-phaseextraction (SPE),22 solid-phase microextraction (SPME),20 liquid-phase microextraction (LPME),17 single drop microextraction(SDME),23 headspace solid-phase microextraction (HSPME),14

dispersive liquid–liquid microextraction (DLLME),24 homoge-neous liquid–liquid microextraction (HLLME),25 ultrasonicassisted headspace single drop microextraction (USA-HSDME),16 vortex-assisted liquid–liquid microextraction(VALLME),26 ultrasound-assisted solvent extraction followedby dispersive liquid–liquid microextraction,27 supercritical fluidextraction combined with dispersive liquid–liquid micro-extraction,18 microwave-assisted extraction-solid-phase extrac-tion,28 or SPE in combination with DLLME29 have been used forthe preparation of water samples containing pesticides.

Solid phase extraction (SPE) has become a well-establishedsample preparation method to extract and preconcentratedesired components.30–33 Application of magnetic nanoparticlesin SPE (MSPE) simplifies sample pretreatment and overcomessome limitations of conventional SPE.34 The sorbent does notneed to be packed into cartridges (as in traditional SPE), and theseparation steps can be carried out easily by applying an externalmagnetic field. Nanoparticles (NPs) possess large surface area,high adsorption capacity, and rapid adsorption rate; so, lowamounts of sorbent and short equilibrium time are required toextract analytes from large volumes of samples.35–37

Magnetic nanoparticles (MNPs) are materials composed of

RESEARCH ARTICLE A.H. Noori, M. Rezaee, M. Kazemipour and H.A. Mashayekhi, 200S. Afr. J. Chem., 2017, 70, 200–208,

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* To whom correspondence should be addressed.E-mail: chem.mashayekhi@toniau.ac.ir

ISSN 0379-4350 Online / ©2017 South African Chemical Institute / http://saci.co.za/journalDOI: http://dx.doi.org/10.17159/0379-4350/2017/v70a27

magnetic elements, including iron, cobalt and nickel. MNPs alsohave certain characteristic properties such as super paramagnet-ism, high coercivity, high magnetic susceptibility and low curietemperature.38 Iron oxide MNPs may exist in different forms,such as magnetite, maghemite, hematite, and goethite or theircombinations, depending on the Fe(²²)/Fe(²²²) ratio, which influ-ences size, composition, morphology, and magnetic propertiesof the particles.39–41 With the latest developments in nano-technology,42 MNPs can be applied for magnetophoretic separa-tion of a wide range of materials41 as they provide several advan-tages over other available separation methods. The advantagesinclude, recyclability for multiple usage, high-throughputprocess, low operational cost, high efficiency, flexible implemen-tation, and scalability.43 These features make MNPs very attrac-tive in many fields such as biotechnology/biomedicine,44 envi-ronmental remediation,45 data storage,46 and other emergingfields. However, unavoidable problems may occur, associatedwith particles in this nanosize range, such as their intrinsic insta-bility/tendency to form aggregates and their interaction withthe (often high ionic strength) media. The inherent magneticforces contribute to the attractive forces among NPs which maylead to aggregation.47,48 Stabilization of MNPs may be achievedby coating the particles, either by chemical bonding or physicaladsorption, with different capping agents. Among the differenttypes of coatings used as sorbents for the extraction of organicanalytes, composites of conductive polymers are of interest.This is due to their multifunctional properties including hydro-phobicity, acid–base character p–p interaction, polar functionalgroups, ion exchange property, hydrogen bonding and electro-activity.49–53

Dispersive liquid–liquid microextraction (DLLME) was intro-duced by Rezaee and co-workers in 2006.54 In this method, anappropriate mixture of extraction and disperser solvents areused. The method has attracted much attention due to its advan-tages such as short extraction time, low consumption of organicsolvent, and simplicity.55–57

In this study, polypyrrole as a conductive polymer was coatedon the surface of Fe3O4 nanoparticles. The samples were firstextracted by magnetic solid phase extraction (MSPE), thenthe eluents were recovered, and subjected to dispersive liquid–liquid microextracton (DLLME) for further purification andenrichment of permethrin and deltamethrin compounds. Theeffect of principle factors such as sorbent amount, extractiontime, extraction solvent, extraction solvent volume, dispersersolvent, disperser solvent volume, and desorption time werestudied.

2. Experimental

2.1. Chemical and ReagentsPermethrin (>98 %) and deltamethrin (99.7 %) were provided

by Sigma-Aldrich (UK). Carbon tetrachloride (>99.5 %),1,1,2-trichloroethane (>98 %), chloroform (>99.8 %), andchlorobenzene (>99 %), as extraction solvents and acetone(>99.8 %), acetonitrile (>99.9 %), ethanol (>99.5 %), and metha-nol (>99.9 %), as disperser solvents were obtained from Merck(Darmstadt, Germany). Double-distilled water was used forpreparation of aqueous solutions. An amount of 0.001 g ofpermethrin and deltamethrin were dissolved in 10.0 mL ofmethanol to obtain standard stock solution with a concentrationof 100 mg L–1. A fresh 10 mg L–1 standard solution containingpermethrin and deltamethrin was prepared in methanol everyweek and stored at 4 °C. Ferric chloride (>98 %), ferrous chloride(99.5 %), sodium hydroxide (>99 %), reagent grade NaCl(>99.5 %) and pyrrole (>97 %) were purchased from Merck.

2.2. InstrumentationThe chromatographic analysis was performed on an Agilent

GC-7890 system equipped with a split/splitless injector systemand flame ionization detector for separation and determinationof permethrin and deltamethrin. Highly pure helium gas(99.999 %, Air Products, UK) was passed through a molecularsieve and oxygen trap (Crs, USA) and was employed as a carriergas with a flow rate of 1.5 mL min–1. The injection port was heldat 290 °C and operated in the splitless mode for 1 min then splitvalve was opened and split ratio of 1:5 was applied. Separationwas carried out on a DB5, 25 m × 0.32 mm i.d. and 0.25 µm filmthickness from SGE (Victoria, Australia) capillary column. Theoven temperature was kept at 230 °C for 5 min and thenincreased to 285 °C at the rate of 10 °C min–1, and was held for10 min. The FID oven temperature was maintained at 300 °C.Hydrogen was generated by hydrogen generator (OPGU-2200S,Shimadzu) for FID at a flow rate of 40 mL min–1. The flow of air(99.999 %, Air Products) for FID was 400 mL min–1. The model2010 D Centurion Scientific centrifuge (Westsussex, UK) wasused for separation of sediment phase from sample solution.

2.3. Preparation of Magnetic Nanoparticles of Fe3O4

The chemical co-precipitation method was used in the prepa-ration of the Fe3O4 NPs [48]. First, a stock solution was preparedby mixing 10.4 g of FeCl3·6H2O, 4.0 g of FeCl2·4H2O, and 1.7 mL ofHCl (12 mol L–1) in 50 mL of deionized water in a beaker. Thesolution was then degassed using nitrogen gas for 20 min beforeuse. Simultaneously, 500 mL of 1.5 mol L–1 NaOH solutionwas degassed (for 15 min) and heated to 80 °C in a reactor. Thesolution of iron salts was then added dropwise using a droppingfunnel for 30 min under nitrogen gas protection with vigorousstirring (1000 rpm) using a glassware stirrer. During the entireprocess, the solution temperature was maintained at 80 °C andnitrogen gas was used to prevent the intrusion of oxygen. Afterthe reaction, the Fe3O4 NPs precipitate obtained was separatedfrom the reaction medium using a magnetic field, and thenwashed four times with 500 mL of deionized water. Finally, theNPs obtained were resuspended in 500 mL of degasseddeionized water.

2.4. Preparation of the PPy/Fe3O4 NanocompositesThe PPy/Fe3O4 nanocomposites were synthesized by in situ

polymerization of the pyrrole (Py) monomer in the presenceof suspended Fe3O4 nanoparticles, using FeCl3 as oxidant atambient temperature. In a typical polymerization technique,0.2 g of Fe3O4 nanoparticles were added to 25 mL deionizedwater in a conical flask and ultrasonicated for 10 min for betterdispersion of Fe3O4 into water. A quantity of 3 g of FeCl3, oxidantwas added to the deionized water containing the Fe3O4

nanoparticles and was shaken for 10 min. To this mixture 0.8 mLof pyrrole was added to the mixture using a syringe. Then thereaction mixture was kept under constant shaking for 3 h atambient temperature. Finally, to stop the reaction, acetone wasadded to the reaction mixture. The black powder obtained wasfiltered and washed with distilled water until the filtrate becamecolourless and finally washed with acetone. Then the compos-ites were dried at 100 °C for 8 h.

2.5. MSPE-DLLME ProcedureTen millilitres of the aqueous sample solution were transferred

to a beaker and spiked at a given concentration of the targetanalytes. Fe3O4@PPy NPs (20 mg) was added into a beakercontaining 10 mL aqueous solution spiked at the level of100 µg L–1 of the analytes, and mechanically stirred for 10 min

RESEARCH ARTICLE A.H. Noori, M. Rezaee, M. Kazemipour and H.A. Mashayekhi, 201S. Afr. J. Chem., 2017, 70, 200–208,

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(Fig. 1a). The magnetic adsorbent was isolated from a solutionusing a magnet (Fig. 1b). Thereafter, the magnetic adsorbent wasmixed with 800 µL methanol using a vortex mixer for 0.5 min(Fig. 1c) and separated using magnet (Fig. 1d), and thereafter theeluent was transferred into a vial for DLLME step. For the extrac-tion process (DLLME), 40 µL of 1,1,2-trichloroethane was addedto the eluent, and then the mixture was rapidly injected into aconical test tube containing 5 mL double-distilled water. Afteragitation for 0.5 min using a vortex mixer, a cloudy solutionresulting from the dispersion of fine droplets of 1,1,2-trichloro-ethane in the aqueous solution was formed in the test tube(Fig. 1f). Then the solution was centrifuged for 5 min at 2000 rpm(Fig. 1g) to force the dispersed fine particles of 1,1,2-trichloro-ethane to sediment at the bottom of the test tube (Fig. 1h). There-after, 2 µL of the organic (1,1,2-trichloroehane) phase wasinjected into GC-FID for analysis.

3. Results and Discussion

3.1. Characterization of Fe3O4@ PPy NanoparticlesThe obtained NPs were stable under these conditions for up to

about one month and were characterized using a transition elec-tron microscope (TEM). The obtained product is shown in Fig. 2.The shape, size and morphology of the synthesized Fe3O4@PPyNPs were determined by TEM and SEM. Furthermore, thecoated PPy was characterized by FT-IR. The shape and size of thenanoparticles were observed by TEM (Fig. 3). The TEM imagesof Fe3O4@PPy particles show that an obvious coating of PPy isimmobilized on the surface of Fe3O4 NPs. The coated PPy layer isclearly seen due to the different electron densities of magneticnanoparticles core (with dark colour) and PPy coating (with lightcolour) in TEM micrograph. The synthesized Fe3O4@PPy NPsshowed a spherical shape with an average diameter of about5–10 nm, however, the nanoparticles tended to aggregate.

In addition, the size and morphology of the resultantFe3O4@PPy NPs were determined by SEM (Fig. 4). TheFe3O4@PPy NPs have a nearly spherical shape with a smoothand uniform surface morphology. Due to agglomeration of theparticles and the lower resolution of SEM in comparison to TEM,

size of the particles in SEM image is larger than that in TEMimage.

The coated PPy was characterized by FT-IR in a range of 4000and 400 cm–1. FT-IR spectra for bare and PPy-coated Fe3O4 NPsare illustrated in (Fig. 5). The characteristic absorption peaks ofFe3O4 NPs, appeared in two spectrums (a and b), correspondingto the stretching vibrations of hydrogen-bonded surface watermolecules and hydroxyl groups at 3400 cm–1 and the Fe—Otransverse vibration at 580 cm–1 were observed. Coating of PPyonto Fe3O4 NPs was confirmed by the appearance of characteris-tic PPy bands in spectrum (b). The weak bands at 2800 and2900 cm–1 were assigned to the stretching vibrations of C—Hbonds. The absorption peak at 1050 and 1314 cm–1 were attrib-uted to the bending vibration of C—H bond in the pyrrole ringand C—N stretching vibration. The absorption bands at 1549and 1460 cm–1 belong to C—C asymmetric and symmetricstretching vibrations of the pyrrole ring, respectively. Theabsorption bands at 2358 and 909 cm–1 belong to C—H vibrationsand the absorption bands at 3737 and 3820 cm–1 belong to N—Hvibrations. These results indicate that PPy has been successfullycoated on the surface of Fe3O4 NPs.

3.2. Effect of Sorbent AmountTo study the effect of sorbent quantity on the extraction

efficiency of permethrin and deltamethrin, different amounts ofsorbent in the range of 10–25 mg were added to the solution(Fig. 6). Finally, an amount of 20 mg of sorbent was found as theoptimum value.

3.3. Effect of Extraction TimeThe extraction recovery strongly depends on the mass transfer

of the analytes from sample solution to the extraction media. Tostudy the effect of this parameter, the extraction was performedin the range of 5–30 min. The extraction time profile forpermethrin and deltamethrin showed that the equilibrium wasreached quite rapidly. The developed method offers a shortextraction time which could be due to the dispersion of sorbentthroughout the sample solution during the extraction and theabsence of internal diffusion resistance. Overall, a duration time

RESEARCH ARTICLE A.H. Noori, M. Rezaee, M. Kazemipour and H.A. Mashayekhi, 202S. Afr. J. Chem., 2017, 70, 200–208,

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Figure 1 NPs was added to the solution and mechanically stirred (a), the magnetic adsorbents were isolated from the solution with the magnet (b),analytes adsorbed were eluted with methanol (c), the eluent was separated from the NPs with the magnet (d), 1,1,2-trichloroethane was added to theeluting solvent of MSPE (e), a cloudy solution resulting from the dispersion of fine droplets of 1,1,2-trichloroethane in the aqueous solution (f), thesolution was centrifuged (g), the organic phase settled in the bottom of the conical test tube (h).

of 20 min was found to be the optimum value for the extractiontime (Fig. 7).

3.4. Effect of Elution Solvent Type and its VolumeIn MSPE-DLLME procedure, the elution solvent used for the

SPE step also plays a role as a disperser solvent during theDLLME stage. For this purpose, acetone, acetonitrile, ethanoland methanol, were selected and tested as elution solvents.The Fe3O4@PPy was eluted using 800 µL of each solvent. The

results (Fig. 8) indicated that the extraction efficiency, whenusing methanol, was more effective than the other potentialelution solvents. Therefore, methanol was selected as the elutionsolvent in further experiments.

To obtain the optimized volume of elution solvent, variousexperiments were carried out using different volumes of metha-nol (700–1000 µL). According to the results shown in Fig. 9, meth-anol volumes lower than 800 µL decreases the extractionefficiency, indicating lower volumes cannot elute the analytes

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Figure 2 TEM image of prepared Fe3O4. Figure 3 TEM images of Fe3O4@PPy.

Figure 4 SEM images of Fe3O4@PPy NPs, (a) ×20 000 (b) ×40 000.

Figure 5 FT-IR spectra of (a) Fe3O4, (b) Fe3O4@PPy.

effectively. Also, at lower volumes of methanol the emulsiondoes not form, thereby the recovery is low. At methanol volumeshigher than 800 µL, the extraction efficiency decreases, dueto the increasing solubility of the target analytes in the waterphase. Therefore, a volume of 800 µL was chosen as the optimumvolume for the elution solvent.

3.5. Effect of Extraction Solvent Type and its VolumeThe extraction solvent must possess certain properties, includ-

ing higher density than water, high extraction capability of theanalytes, and low solubility in water. To investigate the effect ofthe extraction solvent, chloroform, tetrachloroethylene, chloro-benzene, and 1,1,2- trichloroethane were tested. The results

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Figure 6 Effect of adsorbent amount on the extraction efficiency of permethrin and deltamethrin using MSPE-DLLME. Extraction conditions usedwere methanol as disperser or eluent solvent; tetrachloroethylene as the extraction solvent; desorption time of 1 min; extraction time of 10 min;sample volume of 10 mL; and adsorbent amounts of 10, 15, 20 and 25 mg (n = 3).

Figure 7 Effect of extraction time on the extraction efficiency of permethrin and deltamethrin using MSPE-DLLME. Extraction conditions weremethanol as the disperser or eluent solvent; tetrachloroethylene as the extraction solvent; desorption time of 1 min; extraction time of 5, 10, 15, 20, 25and 30 min; sample volume of 10 mL; and 20 mg of adsorbent amount (n = 3).

Figure 8 Comparison of several types of elution and disperser solvent for MSPE-DLLME procedure. Extraction conditions were tetrachloroethyleneas the extraction solvent; desorption time was 1 min; extraction time of 20 min; and sample volume of 10 mL (n = 3).

(Fig. 10) clearly indicate that the extraction efficiency obtainedusing 1,1,2-trichloroethane was higher than that of the otherextraction solvents. It is probably because of the higher solubilityof the analytes in 1,1,2-trichloroethane in comparison withthe other tested solvents. Therefore, 1,1,2-trichloroethane wasselected as the extraction solvent in further experiments.

To examine the effect of the volume of the extraction solvent,additional experiments were carried out using 800 µL methanol(elution solvent) and different volumes of the extraction solvent(20–90 µL), and the results as presented in Fig. 11. It was foundthat with an increase in the volume of 1,1,2-trichloroethane from20.0 to 40.0 µL, extraction efficiency increases and after thatdecreases, because of increasing the volume of the organic (sedi-ment) phase. According to the results, 40.0 µL of 1,1,2-trichloro-ethane was selected as the optimum extraction solvent volume.

3.6. Desorption TimeThe influence of desorption time was also investigated. It was

observed (Fig. 12) that after 5 min, no notable changes occurredin the extraction efficiencies. Therefore, 5 min was consideredas the optimal desorption time of the analytes in subsequentexperiments.

3.7. Quantitative AspectsThe analytical characteristics of the proposed method was

validated under the optimized conditions in terms of linearity,precision and limit of detection to estimate the efficiencyand feasibility of the method for its application in analysis of

environmental samples. The results are listed in Table 1 underoptimum conditions. The analytes demonstrated good linearityin the range of 0.5–100 µg L–1 with good correlation coefficientsr2 = 0.989 and r2 = 0.979 for permethrin and deltamethrin,respectively. The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, was 0.01 µg L–1 for both. The limits ofquantification (LOQs), based on signal-to-noise ratio (S/N) of 10,was 0.6 µg L–1 for both.

The precision of the method was evaluated by carrying outfive independent measurements of the studied compounds atthree concentration levels. The results are shown in the Table 2.

Table 3 compares the proposed method with other extractionmethods for the determination of the target analytes in watersamples. The quantitative results of the proposed method arebetter than those of homogeneous liquid–liquid microextractionvia flotation assistance (HLLME-FA),59 or micro liquid–liquidextraction.60 Comparison of the proposed method with microliquid–liquid extraction and competitive enzyme-linkedimmunosorbent assays (C-ELISAs)61 for the extraction and de-termination of the analytes indicates that this novel method hasa short extraction time for determination of the analytes.C-ELISAs is expensive and requires more organic solvents andtime. Also, micro liquid–liquid extraction requires more toxicorganic solvent and time. Moreover, the proposed method haspotential for the determination of the target analytes in complexmatrices such as waste water due to clean up of the MSPE beforeDLLME method. In addition, it can be used in the large volumesof sample in contrast to the DLLME method. The recovery of

RESEARCH ARTICLE A.H. Noori, M. Rezaee, M. Kazemipour and H.A. Mashayekhi, 205S. Afr. J. Chem., 2017, 70, 200–208,

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Figure 9 Varying the volume of elution solvent using tetrachloroethylene as the extraction solvent, desorption time of 1 min, an extraction time of20 min, and a sample volume of 10 mL (n = 3).

Figure 10 Effect of extraction solvent on recovery of the analytes using methanol as the eluting solvent, a desorption time of 1 min, an extraction timeof 20 min, and a sample volume of 10 mL (n = 3).

the proposed method are comparable with other extractionmethods59–61. Finally, the proposed method has exciting poten-tial to determine the selected analytes at trace levels in watersamples.

3.8. Analysis of Real SamplesDuring the present investigation, matrix effects on the extrac-

tion were also evaluated by investigating the applicability of theproposed method to determine permethrin and deltamethrinconcentrations in waste water, river, tap and well water samples.These samples were extracted using MSPE-DLLME method andanalyzed by GC-FID. The results from waste water, tap, river andwell water samples showed that they were free of permethrinand deltamethrin contamination. These samples were spiked

with permethrin and deltamethrin standard solution (10.0 µg L–1

concentration level) to assess matrix effects. The results of rela-tive recoveries were between 88 to 95 %. These results (Table 4)show that the waste water, tap, well and river water matrices, inour present context, had negligible effect on MSPE-DLLMEmethod.

4. ConclusionThis paper describes the application of the MSPE-DLLME

method combined with GC-FID for determination of traceamounts of permethrin and deltamethrin in water samples. Therelative recoveries were in the range of 88–95 % and showed thatwaste water, tap, well and river waters matrices had negligibleeffect on the MSPE-DLLME. The method is precise, reproduc-ible and linear over a wide range and require small volumes oforganic extractant. Moreover, the proposed method is promising

RESEARCH ARTICLE A.H. Noori, M. Rezaee, M. Kazemipour and H.A. Mashayekhi, 206S. Afr. J. Chem., 2017, 70, 200–208,

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Figure 11 Varying the volume of the extraction solvent during the DLLME step. Methanol was used for the MSPE stage with a desorption time of1 min, the extraction time was 20 min, and the sample volume was 10 mL (n = 3).

Figure 12 Effect of desorption time on the extraction efficiency of MSPE-DLLME of permethrin and deltamethrin using methanol as the disperseror eluent solvent; 1,1,2-trichloroethane as the extraction solvent; desorption time of 0.5, 1, 5, 7 and 10 min; extraction time of 20 min; and a samplevolume of 10 mL (n = 3).

Table 2 Relative standard deviation at three different concentrationlevels by using proposed method.

Analyte Relative standard deviation (R.S.D.%), n = 5

5.0 µg L–1 10.0 µg L–1 50 µg L–1

Permethrin 6.5 4.6 1.0Deltamethrin 8.6 5.3 1.5

Table 1 Quantitative results of MSPE-DLLME and GC-FID method forpermethrin and deltamethrin.

Analyte Linear range LOD a LOQ b R2 c

/µg L–1 /µg L–1 /µg L–1

Permethrin 0.5–100 0.01 0.6 0.989Deltamethrin 0.5–100 0.01 0.6 0.979

a LOD, limit of detection for S/N = 3.b LOQ, limit of quantification for S/N = 10.c Coefficient of determination.

for trace analysis of permethrin and deltamethrin in naturalwater samples.

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Table 4 Determination of permethrin (PRM) and deltamethrin (DLM) in waste water, river, tap and well water and relative recovery of spikedpermethrin and deltamethrin in them.

Sample Concentration of PRM and DLM Added PRM and DLM Found PRM and DLM Relative recovery/µg L–1 ± S.D., n = 3 /µg L–1 /µg L–1 ± S.D., n = 3 /%

PRM DLM PRM DLM PRM DLM PRM DLM

Tap water a n.d b n.d b 10 10 9.2 ± 0.1 9.3 ± 0.2 92 93Waste water c 2.1 1.8 10 10 10.9 ± 0.5 10.7 ± 0.6 88 89Well water d n.d b n.d b 10 10 9.4 ± 0.2 9.1 ± 0.3 94 91River water e n.d b n.d b 10 10 9.5 ± 0.3 9.2 ± 0.4 95 92

a From drinking water system of Tehran, Iran.b Not detected.c From Tehran, Iran.d From Tehran, Iran.e Kolakchal River water, Tehran, Iran.

Table 3 Comparison of the proposed method with other extraction methods for determination of deltamethrin and permethrin.

Method R.S.D.% Dynamic linear range Limit of detection Extraction time Recovery/µg L–1 /µg L–1 /min /%

HLLME-FA-GC-FID59 6.9–7.8 1.0–200 0.2–0.3 1 90–98

Micro-liquid–liquid extraction-GC-MS60 1.9–11.7 1.0–9.0 0.003–0.035 13 >93

Competitive enzyme-linked immunosorbent – 0.2–150 1.1 72 h 92–100assays (C-ELISAs)61

MSPE-DLLME-GC-FID 1.0–1.5 0.5–100 0.01 1 88–95

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